In communication systems, such as cable systems which distribute television and other signals over a large area, there are typically many components utilized in providing communication of signals between a source, such as at a cable plant, and receivers, such as at individual subscriber premises. However, such communication systems and their attendant components often introduce errors into the transmitted signals, such as signal distortion. For example, cable television signals are broadband (e.g., 50 MHz to 1 GHz), typically including as many as 100 frequency division television channels, and are often subject to network introduced tilt (non-uniform frequency response) over the frequencies of the communicated band.
Accordingly, cable distribution systems today implement devices, such as amplifiers and equalizers, to provide correction of tilt within the network band. For example, to provide tilt correction, a cable distribution system may employ amplifiers and equalizers distributed throughout the network. However, such tilt correction is generally provided for tilt correction at the point in the network the particular tilt correction device is deployed. Accordingly, even with a perfectly calibrated system, an amount of tilt is present in the signals as received by individual subscribers. For example, subscribers typically experience tilt associated with the network components deployed in the signal path disposed between each particular subscriber and a last tilt correction device in the network. Because each subscriber experiences an appreciably different signal path in this “last mile,” it is typically not possible to compensate for the tilt assosicated with the last mile using typical deployment of correction devices.
Moreover, the amount of tilt correction provided by such devices must be calibrated to correspond to the amount of tilt experienced in the signal in the signal path leading to the tilt correction device. Introduction of additional components into this signal path, failure of particular components, and even time and temperature related operational changes may result in less than optimal tilt correction in the network. Recalibration of such devices typically requires dispatching of service personnel to the appropriate device locations.
There are presently no devices allowing the cable plant to verify maintenance or monitor the performance of the devices providing tilt correction in the system. Accordingly, if there is a problem in the cable network, the cable operator must typically rely upon the subscribers calling the cable plant with a trouble report. Only by these calls will the cable plant identify that there is a problem in the system and, often through correlating the location of the subscribers complaining and the types of complaints being registered, will the cable operator be able to isolate the source of the problem and, thus, dispatch service personnel to the appropriate location.
Accordingly, a need in the art exists for systems and methods which provide for signal calibration, such as signal tilt correction/calibration, for individual subscriber premises. A further need exists in the art for such systems and methods to provide feedback to a centralized operations center, such as a cable plant, with respect to calibration.